<!DOCTYPE html>
<html lang="en">
  <head>
      <meta charset="UTF-8">
      <title>Title</title>
      <style>
        #d1{
          width: 100px;
            height: 100px;
          border: 1px solid black;
        /*  指定方向添加外边距*/
        /*  margin-left:100px ;*/
        /*  margin-top: 50px;*/
        /*  margin-bottom:50px;*/
        /*  四个方向同时赋值*/
        /*  margin:50px ;*/
        /*  上下50px左右100px*/
        /*  margin:50px 100px;*/
        /*!*  上右下左 顺时针赋值*!*/
          margin: 10px 20px 30px 40px;
        }
        #d2{
          width: 100px;
          height: 100px;
          border: 1px solid black;
        /*外边距塌陷：兄弟元素上下相邻，彼此添加的外边距取最大值  */
          margib-top:50px;
        }
        #s1{
          margin-right: 50px;
        }
        #s2{
          margin-left: 30px;/*左右相邻彼此相加*/
        }
        #big{
          width: 200px;
          height: 200px;
          background-color: cyan;
          /* 解决外边距粘连问题*/
          overflow: hidden;
        }
        #big>div{
          width: 50px;
          height: 50px;
          background-color: red;
          margin-left: 50px;
          /*外边距塌陷：父子级元素上边缘重叠时，给元素添加的外边距取最大值  */
          margin-top: 50px;
        }
      </style>
  </head>
  <body>
      <div id="big"><div></div></div>
      <span id="s1">span1</span>
      <span id="s2">span2</span>
      <div id="d1">div1</div>
      <div id="d2">div2</div>
  </body>
</html>